As part of the control for a gas turbine engine there is often a need to measure pressures at different points of the engine. Pneumatic pressure signals are routed to pressure sensing assemblies via pipes and connected to pressure manifolds of the assemblies.
In such assemblies, efforts are made to avoid moisture propagation down the pipes as this can affect the pressure readings.
As the operating environment of the engine mounted pressure sensing assemblies is generally not controlled, there is potential for residual moisture to form ice either within the sensors of an assembly or within its manifold. Ice within the sensors can lead to a pressure measurement error or a damaged sensor. Ice within the manifold can block the pressure signal leading to fault messages from the sensor. However, when investigated further, such messages can lead to ‘fault not found’ issues, since once the assembly has returned to ambient temperature any ice that had formed will have melted and any residual moisture evaporated.
To protect against this issue some pressure sensors contain in-built heaters that may be used to raise the internal sensor temperature and thereby preventing the formation of ice. Adding heaters to the pressure sensors reduces the possibility of ice causing a pressure reading error but does not rule out the possibility of blockages in the pressure manifold. Additional power, which can be as high as 5 W per sensor, is also required to drive the sensor heaters. The activation of heaters within pressure sensor assemblies also leads to a thermal shock, potentially reducing sensor reliability.